Spectators watch the League of Legends North American championship series spring round robin competition in California. Photograph: Robyn Beck/AFP/Getty Images

Professional video game playing is becoming a global spectator sport, according to a study which says 2.4bn hours were spent watching gamers last year.

A report from research firm IHS Technology suggests that e-sports, or watching other people play games, is far from a niche interest. The company says the number of e-sport viewing hours nearly doubled, from 1.3bn in 2012 to 2.4bn in 2013.

Games fans watch people play online through services such as Twitch – which is a $1bn takeover target for Google – and on traditional TV channels or at live events.

Dan Cryan, author of the IHS report, said that e-sports videos had "rapidly transformed from a niche activity into a widely watched, global, cross-platform entertainment category".

The report picks out Dota 2, League of Legends and StarCraft II as the most popular games being watched, with factors such as the emergence of online video sites leading to the rapid growth in e-sports viewing globally.

"Key game titles have reached maturity and game publishers are taking a major role in promoting e-sports competitions. Furthermore, e-sports viewing has been boosted by the emergence of online video platforms that are capable of handling large-scale live audiences," he said.

Twitch has more than doubled its monthly audience from 20 million at the end of 2012 to 45 million at the end of 2013. On average people have been watching 106 minutes a day.

Its biggest audience occurred in October, with 32 million people watching the League of Legends Season 3 world championship event in a single day.